None.
The present invention relates to the fabrication of three-dimensional objects using additive process modeling techniques. More particularly, the invention relates to modeling machines which form three-dimensional objects by depositing modeling material onto a substrate mounted to a modeling platform.
Additive process modeling machines make three-dimensional models by building up a modeling medium, usually in planar layers, based upon design data provided from a computer aided design (CAD) system. A mathematical description of a physical part to be created is split into (usually) planar layers, and those layers are individually shaped and applied to produce the final part. Three-dimensional models are used for functions including aesthetic judgments, proofing the mathematical CAD model, forming hard tooling, studying interference and space allocation, and testing functionality. The dominant application of layered manufacturing in recent years has been for rapid prototyping.
Examples of apparatus and methods for making three-dimensional models by depositing solidifiable modeling material are described in Crump U.S. Pat. No. 5,121,329, Batchelder, et al. U.S. Pat. No. 5,303,141, Crump U.S. Pat. No. 5,340,433, Batchelder, et al. U.S. Pat. No. 5,402,351, Crump et al. U.S. Pat. No. 5,503,785, Abrams et al. U.S. Pat. No. 5,587,913, Danforth, et al. U.S. Pat. No. 5,738,817, Batchelder, et al. U.S. Pat. No. 5,764,521 and Comb et al. U.S. Pat. No. 5,939,008, all of which are assigned to Stratasys, Inc., the assignee of the present invention. An extrusion head extrudes solidifiable modeling material in a fluent strand (also termed a xe2x80x9cbeadxe2x80x9d or xe2x80x9croadxe2x80x9d) from a nozzle onto a base. The base comprises a modeling substrate which is removably affixed to a modeling platform. The extruded material is deposited layer-by-layer in areas defined from the CAD model, as the extrusion head and the base are moved relative to each other by mechanical means in three dimensions. The finished model is removed from the substrate. A solidifiable material which adheres to the previous layer with an adequate bond upon solidification is used as the modeling material. Thermoplastic materials have been found particularly suitable for these deposition modeling techniques.
Other additive process manufacturing techniques include depositing UV curable polymers as in Masters U.S. Pat. No. 5,134,569; jetting of droplets of material as in Helinski U.S. Pat. No. 5,136,515; extruding a seable plastic in vertical strips as in Valaaara U.S. Pat. No. 4,749,347; laser welding deposition as in Pratt U.S. Pat. No. 5,038,014; stacking and adhering planar elements as in DiMatteo U.S. Pat. No. 3,932,923; and applying shaped layers of paper as in Hull U.S. Pat. No. 5,192,559.
In additive process three-dimensional modeling machines utilizing manufacturing techniques such as those described above, the model is built up on a base comprising a substrate mounted on a modeling platform. The material being deposited must adhere to the substrate to form a foundation layer over which the remaining layers of the object are deposited. The substrate stabilizes the model as it is built up, and facilitates removal of the model from the modeling machine when the model is complete.
It is preferred that parts deposited on the modeling substrate be strongly adhered thereto to overcome two effects. First, strains generated within the extruded material tend to warp the deposited structures unless the structures are supported in their correct orientation. The substrate is important in serving to avoid localized shrinkage in the foundation layer. Second, in some deposition processes, there are forces such as pull from an extrusion nozzle and centripetal acceleration on parts that are not stationary, that tend to distort the deposited structures. A delamination of the foundation layer from the substrate during the building of the object could result in a total failure in forming the object. Further, since the removable substrate becomes a defining surface for the object being built, it must be held in a well-defined configuration. Typically, the substrate is held in a configuration approximating a plane.
The Crump ""329 and ""433 patents disclose a foam plastic material for use as a modeling substrate. A blue polystyrene material manufactured by Dow-Corning Corp. under that name and having a compression strength of 30 psi is identified as particulary suitable coarse, porous structure. The Crump ""329 and ""433 patents also disclose modeling on a wire mesh sandpaper substrate, and on a water soluble wax. The Batchelder et al. ""521 patent discloses a sheet of magnetic material for use as a modeling substrate, wherein the modeling platform includes a magnet for attracting the sheet, while the Comb ""008 patent discloses a flexible sheet substrate held down by vacuum forces.
In rapid prototyping systems sold in the past by Stratasys, Inc., a preferred substrate material has been a polymer foam. A foam slab substrate has proven particularly suitable for supporting models made by extrusion-based deposition modeling techniques. The porosity and compressibility of foam allows foundation layers of modeling material to be buried into the foam, which increases stability of the model as is it built up. The foam substrate is mounted onto a tray outside of the modeling machine. Up to eight spears are inserted through side walls of the tray and pressed into the foam to engage the foam from all sides. The tray is then placed on the modeling platform within the modeling machine, and locked into place. After the object is formed, the tray is removed from the modeling machine and the foam is broken away from the object.
While foam substrates have found substantial use, mounting the foam into a modeling machine with spears requires the user to spend time that could be better spent modeling. Additionally, the spears can be lost when not in use. Further, the foam materials used in the prior art produce dust when broken away from the object. The presence of dust creates a risk that the dust may contaminate bearings and bushings in the modeling machine.
The present invention is an apparatus and method for mounting a substrate to the modeling platform of a machine that builds up three-dimensional objects of predetermined design depositing solidifiable material on the substrate. The substrate mounting system of the present invention includes two parallel rails positioned on opposite sides of a modeling platform. A blade extends along each rail, each blade having an inward-facing knife edge. A slab substrate having a width which approximates the distance between the two rails and having slits in its sides is loaded in the machine by lining up the slits with each knife edge and pushing the slab towards the rear of the platform as the knife edges penetrate the slab. Preferably, the platform includes a rear stopper to stop rearward motion of the substrate. The platform preferably also includes a retainer or retainers at its front edge that lift up to lock the substrate into place on the platform during modeling. The substrate is removed from the platform by releasing the front edge retainers, if any, grasping the substrate, and sliding the substrate towards the front of the platform.